Anomalous behavior or ribonuclease A on Sephadex G-100

Ribonuclease A was found to behave in an unusual fashion on a Sephadex gel column. Though ribonuclease A produces a single, well-defined protein peak on elution, enzyme activity can be detected several void volumes after the protein peak. A second unrelated protein added to the column will displace further activity as will 0.5 M phosphate buffer. This additional activity, apparently due to ribonuclease A or an active fragment of the enzyme, would appear to make this enzyme unsuitable for use as a standard in molecular weight determinations of other nucleases.